Excerpt: If you want your retirement nest egg to last as long as you do, the general rule of thumb is that you should withdraw 4% of the initial value of your diversified portfolio, adjusted each year for inflation. With that rate, you can be fairly confident that you won't run out of cash before you leave this world. Only there's one small problem. That 4% rule means that for every $10,000 in income you're trying to replace, you'll need to have $250,000 worth of savings. To replace, say, a $40,000 salary, you'll have to amass a cool $1 million.  MORE >>